OutInform: Houston Pride Guide 2017 Issue | Page 11

transmission more likely, in fact, did not make the slightest
bit of difference.
Are women more vulnerable than men? Zero transmissions
in both genders. Is anal sex riskier than vaginal sex? Zero
transmissions for both. Is it riskier to be the bottom than
the top? Zero transmissions for bottoms and for tops.
Do sexually transmitted infections increase the risk? Zero
transmissions in people with sexually transmitted infections.
We should add that 11 of the HIV-negative partners did
acquire HIV, but from somebody else. Careful analysis
showed that in all 11 cases, the virus was genetically
different enough from their partners' virus to indicate that
they must have contracted it from another person -- from
outside their main relationship.
Reporting their results in the prestigious Journal of the
American Medical Association last year, the researchers
summed it up: "The estimate of the overall transmission
rate, and the transmission rate for anal sex, was zero."
With the consequences of 58,000 unprotected sex acts
already recorded, the findings are robust. In science, having
a larger number of observations or study participants
generally boosts the certainty with which scientists can
state their conclusions. In statistics, this is expressed
through something called the 95% confidence interval.
However, because the first phase of the PARTNER study
had fewer gay couples than heterosexual couples,
researchers have less data on anal sex than vaginal sex.
To remedy this, a second, ongoing phase of the study
is collecting more data on only gay couples. There's no
indication that the researchers expect this to reveal any
cases of transmission during anal sex when viral load was
undetectable. It's more likely to increase the certainty and
scientific rigor with which the researchers can state that,
with undetectability, the transmission rate during anal sex
is zero.
The HPTN 052 Study
group. But what about those three people who picked up
HIV from his or her partner, even though they had been
prescribed HIV treatment?
In each case, the HIV-positive partner did not have an
undetectable viral load. The transmission occurred either
within the first three months of taking treatment (before viral
load had been durably suppressed) or after HIV treatment
had failed and viral load had risen to detectable levels. "No
linked infections were observed when HIV-1 infection was
stably suppressed by [antiretroviral treatment] in the index
participant," Myron Cohen, M.D., and colleagues reported in
New England Journal of Medicine last year. So, while the 93%
figure is some way off 100% effectiveness, it relates to the
reduction in transmissions when HIV treatment is provided
early, not the reduction when HIV treatment results in an
undetectable viral load.
Transformative Evidence
How to sum up this scientific evidence? Demetre Daskalakis,
M.D., M.P.H., assistant commissioner for the Bureau of HIV/
AIDS at the New York City Health Department put it like this:
Several strong lines of evidence indicate that consistent viral
suppression is truly HIV prevention.
Given these empiric findings, New Yorkers living with
HIV who take their antiretrovirals consistently and have
suppressed viral loads should be confident that their risk of
HIV transmission is negligible.
According to Matthew Hodson of NAM aidsmap:
This understanding transforms the way that HIV is considered
with enormous implications for what it now means to live
with HIV and the best ways to prevent it. The fear of catching
HIV from a sexual partner fuels HIV stigma, which is why it's
so important that the 'undetectable equals untransmittable'
message is heard and understood.
The other key scientific study is known as HPTN 052. This
randomized controlled trial (perhaps the most reliable
scientific method) recruited 1763 mostly heterosexual
couples with mixed HIV status. The HIV-positive partners
were randomly allocated either to start HIV treatment
immediately or to delay treatment until their CD4 count
was considerably lower.
Again, the researchers were interested in how many
HIV-negative partners wound up acquiring HIV from their
HIV-positive partner. The direct comparison of couples
who had immediate access to HIV treatment and couples
who had to wait for it tells us about the difference that
providing HIV treatment makes.
Forty-six individuals acquired HIV from their primary
partner during the trial, three in the immediate-treatment
arm and 43 in the delayed-treatment arm. This amounts
to 93% fewer transmissions in the immediate-treatment
p